The present invention concerns a catalyst component for polymerization catalysts of .alpha.-olefines, such catalysts comprising an organoaluminum compound, an electron donor, and a solid catalyst component. More particularly, the solid catalyst component is obtained when a component or compound containing magnesium reacts with a titanium halogen compound. The present invention also concerns a method for producing these catalyst components, as well as a method for polymerizing .alpha.-olefines, especially propylene, utilizing these thus-produced catalyst components.
High-activity catalysts which are produced from an aluminum alkyl compound, an electron donor, and a halogenated titanium compound on a solid carrier containing various magnesium compounds, are known for polymerizing .alpha.-olefines. The most commonly used magnesium compound is anhydrous magnesium chloride, either alone or together with other magnesium compounds, or organic magnesium compound manufactured by halogenating organic magnesium compounds with compounds containing chlorine. The magnesium compound may also be included in the solid carrier component for which silica is most commonly used.
In these types of polymerization catalysts, the properties of the solid carrier component have significant influence upon the properties of the final catalyst, e.g. on the activity thereof. These properties can be essentially influenced by the method of producing the carrier components.
It has been noted in the present invention, that when polymerizing .alpha.-olefines, especially propylene, it is possible to obtain considerably better yields and isotactic values, if silica is replaced by magnesium silicate as the solid carrier component, and further, if certain procedures are adopted in the manufacturing of the catalyst component.
The use of magnesium silicate in Ziegler-Natta catalysts, is known in and of itself. Thus, for example, according to the method presented in British patent publication No. 2,082,602, magnesium alkyl is dissolved or suspended into an inert hydrocarbon solvent, with magnesium silicate being added, after which the obtained solid catalyst compound is washed and treated with titanium tetrachloride. The thus-produced catalyst is used in the homopolymerization and copolymerization of ethylene.
In the method presented in DE patent publication No. 3,011,326, magnesium halide, e.g. magnesium chloride, is dissolved in ethanol, with magnesium silicate treated with a chlorinating agent being added into the produced solution. The magnesium halide is precipitated by adding the mixture into a hydrocarbon solvent, e.g. heptane, with the thus-obtained component being treated with titanium tetrachloride. The thus-produced catalyst has been also applied in the polymerization of propylene, however the isotactic value obtained for the polymer in this method ranges between 92-93%.